MAGNETICALLY STABILIZED SURFACE ALLOYS

We investigate the interrelation of magnetism and stability of ultrath in magnetic films and come to the conclusion that under certain circum stances there should exist magnetically stabilized two-dimensional sur face alloys. We present ab initio results for the formation energy and the interdiffusion energy of Cu(001)c(2 x 2) 3d surface alloy films. Results based on the density functional theory in the local spin densi ty approximation (LSDA) indicate the existence of a thermodynamically stable surface alloy. Cu(001)c(2 x 2) Mn. Although in detail, the resu lts depend on the Cu substrate, the trends presented below have an uni versal character. Therefore, Cu(100)c(2 x 2) Mn is only an example of a much wider class of magnetic surface alloys. Recently, several of th ese surface alloys have been found experimentally, showing an unexpect ingly large structural corrugation of the surface alloy atoms. This wi ll be discussed as a result of a large magneto-volume effect. We found in addition a non-magnetic surface alloy Ti/Cu(001), which is not yet confirmed experimentally. Total energy calculations were carried out using the full-potential linearized augmented planewave (FLAPW) method in him geometry.